Tank-type trickling filters and methods for cleaning treated water tanks in tank-type trickling filters.

Abstract

The invention relates to a trickling filter (1) comprising a reaction tank (20) and a treated water tank (30), wherein the reaction tank (20) comprises a straight box-shaped casing (21) with airtightness, a mesh bottom plate (22) arranged at the bottom of the casing (21), and a carrier (23) filled in the casing (21), and the treated water tank (30) comprises a box-shaped body (30A) comprising a rectangular bottom plate (31) inclined in the treated water discharge direction and side walls (32 to 35), the water tank section (36) arranged in the treated water discharge direction of the body (30A), a baffle (37) arranged in the water tank section (36), an air drain (38), a treated water drain (40), and a solids drain (41).

Description

Container-type trickling filter device and method for cleaning the treated water tank in the container-type trickling filter device

[0001] The present invention relates to a trickling filter device in a wastewater purification system that purifies wastewater such as industrial wastewater, water supply and sewage, and river water. More specifically, the present invention relates to a container-type trickling filter device in which microorganisms are attached to a trickling filter bed in which filter media blocks (microorganism-holding carriers) are stacked in layers within a reaction tank, wastewater is sprayed over the trickling filter bed, and treated water that has permeated and flowed down is removed from the treated water tank, and a method for cleaning the treated water tank in a container-type trickling filter device.

[0002] Trickling filters have long been used as a method for purifying wastewater. A typical trickling filter consists of a reactor, a trickling device installed above the reactor, and a treated water tank that receives and stores the treated water that has passed through the reactor. The reactor is filled with microorganism-retaining carriers to which microorganisms contained in the wastewater adhere, and the collection of these microorganism-retaining carriers forms a trickling filter. The wastewater is trickled from above and flows from top to bottom within the reactor by gravity. The treated water, purified by the microorganism-retaining carriers, falls and accumulates in the treated water tank below. Such trickling filters have the advantages of low power consumption, easy operation and management, and low sludge generation.

[0003] As an example of a microorganism-holding carrier in the above-mentioned wastewater purification device, the applicant has applied for a water purification device configured to fill a sponge carrier in a reaction tank, pour treated water down (sprinkle water), take in air around the sponge carrier, and have the microorganisms in the carrier use the air to oxidize organic matter and ammonia in the wastewater, thereby purifying the wastewater (Patent Publication No. 2019-171237).

[0004] Depending on the location of the trickling filter device, the device is enclosed to prevent the infestation of insects such as moth flies, and a fan is used to supply air inside the device to ventilate the device. In a typical structure, ventilation is achieved by drawing air in from below the reaction tank (20) using a fan. This prevents the odor of wastewater from leaking directly from the trickling filter contained within the device. Solids that are not captured by the trickling filter fall into the treated water tank along with the treated water. If these solids fall and remain in the treated water tank for a long period of time, they will decay and pollute the treated water, so they must be discharged. In conventional trickling filter devices, the treated water tank below the trickling filter is large and deep enough to allow a certain amount of solids to accumulate. The bottom of the treated water tank is sloped by approximately 20% to promote solids discharge, and the accumulated solids are discharged through a solids extraction pipe located near the bottom of the treated water tank. Alternatively, the solids can be collected using a scraper or similar device, and then discharged when a certain amount of solids has accumulated.

[0005] Japanese Patent Publication No. 2019-171237

[0006] Trickling filter systems, which offer advantages such as low power consumption, easy operation and management, and low sludge production, are expected to become more widespread in developing and underdeveloped countries as environmental pollution issues become more serious. One possible method for widespread adoption is to incorporate them into marine transport containers and export them. Containerized trickling filter systems can be manufactured in domestic factories, transported by sea to the site, installed, and connected to piping for wastewater and treated water, enabling rapid use. However, marine transport containers are subject to size restrictions, and the system must comply with these regulations. Meanwhile, ensuring sufficient trickling filter capacity is important to ensure sufficient microbial content in the trickling filter, which contributes to wastewater purification. Furthermore, as mentioned above, while conventional trickling filter systems have a large and deep treatment tank below the trickling filter, incorporating a trickling filter system into a marine transport container, which is subject to size restrictions, does not allow for a sufficient slope at the bottom of the treatment tank to promote solid discharge. If discharge is not promoted, measures will be needed to prevent the generation of foul odors due to the decay of solid matter. Furthermore, when installing a conventional scraper, space must be secured for auxiliary equipment such as a drive unit.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a trickling filter device that can automatically discharge solids accumulated in the treatment tank below the trickling filter without using a scraping machine or other machinery, and that can be incorporated into a sea transport container that is subject to dimensional regulations.

[0008] The inventors have solved the above problems by the following means: [1] A trickling bed device (1) comprising a reaction tank (20) and a treated water tank (30), wherein the reaction tank (20) comprises an airtight rectangular parallelepiped housing (21), a mesh-like bottom plate (22) attached to the bottom of the housing (21), and carriers (23) packed inside the housing (21), and the treated water tank (30) comprises a box-shaped main body (30A) comprising a rectangular bottom plate (31) inclined in the direction of discharge of treated water and side walls (32-35), a water tank section (36) attached to the main body (30A) in the direction of discharge of treated water, a weir (37) attached to the water tank section (36), an air withdrawal pipe (38), a treated water withdrawal pipe (40), and a solids withdrawal pipe (41). [2] The container-type trickling filter apparatus according to [1], characterized in that a circulating treated water withdrawal pipe (42) is provided in the water tank section (36). [3] The container-type trickling filter apparatus according to [2], characterized in that an overflow trough (43) is provided in the treated water tank (30), and a partition plate (44) is movably provided between the treated water withdrawal pipe (40) connected to the overflow trough (43) and the circulating treated water withdrawal pipe (42). [4] The container-type trickling filter apparatus according to any one of [1] to [3], characterized in that a drain pipe (45) for discharging water pools from the air withdrawal pipe (38) is provided midway in the air withdrawal pipe (38). [5] The container-type trickling filter apparatus according to any one of [1] to [4], characterized in that the air withdrawal pipe (38) is inclined so that the tip 38a of the air withdrawal pipe (38) is downward. [6] The container-type trickling filter apparatus according to any one of [1] to [5], characterized in that the bottom plate (31) of the treated water tank (30) has a slope of at least 1 / 100 toward the discharge portion of the treated water. [7] The container-type trickling filter apparatus according to any one of [1] to [6], characterized in that the treated water tank (30) of the trickling filter apparatus (1) is used as a civil engineering structure, and the space occupied by the treated water tank (30) is replaced with the capacity of the reaction tank (20) of the trickling filter apparatus (1) within the dimensional regulations of a marine transport container, thereby increasing the capacity.[8] The container-type trickling filter apparatus according to [7], characterized in that the reaction tank (20) is composed of a plurality of stages of the housings (21), and the height and volume of the trickling filter apparatus (1) can be changed by changing the number of the housings (21). [9] A method for cleaning the treated water tank (30) of the container-type trickling filter apparatus according to any one of [1] to [8], characterized in that, when extracting solids, the valve of the solids extraction pipe (41) is opened to discharge all of the treated water accumulated in the treated water tank (30), and then, while the wastewater is being sprayed onto the trickling filter, the treated water that passes through the filter bed and drips into the treated water tank (30) is showered to send the accumulated solids on the bottom plate (31) together with the treated water toward the weir (37) even at a gentle incline close to horizontal.

[0009] According to the present invention having the above configuration, in a container-type trickling filter device, solids accumulated in the treatment tank can be automatically discharged without using machinery, etc., and a trickling filter device can be provided that is incorporated into a sea transport container that is subject to dimensional regulations.

[0010] FIG. 3 is a perspective side view of an embodiment of a container-type trickling filter bed apparatus of the present invention. FIG. 4 is a front view of an embodiment of a container-type trickling filter bed apparatus of the present invention. FIG. 5 is a plan view of an embodiment of a container-type trickling filter bed apparatus of the present invention. FIG. 6 is a side view of an embodiment of a container-type trickling filter bed apparatus of the present invention. FIG. 7 is a cross-sectional view of FIG. 3, a cross-sectional view of FIG. 4, a cross-sectional view of FIG. 4, a diagram showing another embodiment of a container-type trickling filter bed apparatus of the present invention. FIG. 8 is a diagram showing another embodiment of a container-type trickling filter bed apparatus of the present invention. FIG. 9 is a diagram showing another embodiment of a container-type trickling filter bed apparatus of the present invention. FIG. 10 is a diagram showing another embodiment of a container-type trickling filter bed apparatus of the present invention.

[0011] The mode for carrying out the present invention will be described with reference to the drawings of the embodiments. Figure 1 is a perspective side view of an embodiment of a container-type trickling filter device of the present invention, an example in which a marine transport container is used as the outer frame, Figure 2 is a front view of an embodiment of a container-type trickling filter device of the present invention, Figure 3 is a plan view of an embodiment of a container-type trickling filter device of the present invention, Figure 4 is a side view of an embodiment of a container-type trickling filter device of the present invention, Figure 5 is a cross-sectional view A-A of Figure 3, Figure 6 is a cross-sectional view B-B of Figure 4, Figure 7 is a cross-sectional view C-C of Figure 4, and Figures 8 and 9 are diagrams showing other embodiments of a container-type trickling filter device of the present invention. In Figures 1 to 11, 1 is a trickling filter device, 20 is a reaction tank, and 30 is a treated water tank. In the embodiment of the present invention, the frame (51-54) of a marine transport container is used to facilitate marine transportation of the container-type trickling filter device. However, this is not limited to this. A feature of the present invention is that the container-type trickling filter device can reduce the size of the treated water tank 30 and discharge treated water and solids without the use of machinery such as a scraper. The reaction tank 20 comprises an airtight rectangular parallelepiped housing 21, with a mesh-like bottom plate 22 horizontally attached to the bottom of the housing 21. A sponge carrier 23 (also referred to as the carrier 23 in the present invention) is filled on top of the bottom plate 22. The sponge carrier 23 is a porous body with an open-cell structure, formed from a material that has water retention and flexibility. As shown in FIG. 11 , in this embodiment, the sponge carrier 23 is composed of a porous body 24 having gaps through which microorganisms can adhere and a frame 25 that houses the porous body 24. The porous body 24 can be made of a foamed resin, such as a urethane resin, an ester polymer, or an ether polymer. Wastewater is sprayed onto the sponge carrier 23 inside the housing 21 from a spray nozzle (not shown) provided at the top of the trickling filter device. The sprayed wastewater moves downward by permeating the porous body 24 of the sponge carrier 23 or passing over the surface of the porous body 24, during which time the wastewater is purified by the microorganisms attached to the porous body 24 and drips from below the trickling filter as treated water.At this time, the air penetrates into the porous body 24 through the openings 25a in the frame 25, and oxygen and other substances dissolved in the liquid from the air supplied to the gaps between the carriers are efficiently supplied to the microorganisms present inside the porous body 24, thereby purifying the wastewater. Reference numeral 26 denotes a space for connecting piping and a ladder used to access the upper part of the device for inspection work, and 27 denotes an inspection hatch for inspecting the interior of the reaction tank. As described below, when air is drawn into the treatment tank 30 through an air vent pipe 38 installed in the treatment tank 30 by a fan or the like (not shown), the oxygen-containing liquid penetrates through the surface of the sponge carrier 23 in the housing 21 of the reaction tank 20, supplying oxygen and other substances to the sponge carrier 23 in the housing 21 of the reaction tank 20. While sponge is used here as a suitable carrier, it is not necessary to use a sponge carrier 23 as the material for the porous body 24. For example, instead of the carrier 23, stone or hard resin, which is generally used as a filter material for water treatment, may be used.

[0012] The treated water tank 30 comprises a box-shaped main body 30A made up of a rectangular bottom plate 31 and side walls 32-35, and separates treated water and solids such as sludge discharged from the reaction tank 20. The treated water tank 30 is provided with a water tank section 36 that collects and discharges treated water and solids such as sludge discharged from the reaction tank 20. Furthermore, since the treated water tank 30 discharges not only purified treated water but also solids contained in the treated water, the inclination of the bottom plate 31 must be such that the treated water and solids discharged into the treated water tank 30 slide over the bottom plate 31 under their own weight and are transported from the side walls 33 toward the water tank section 36. However, if the inclination angle of the bottom plate 31 is large, the height of the treated water tank 30 must be increased, which may be subject to dimensional restrictions imposed on marine transport containers. Considering the need to minimize the height of the treatment tank 30, it is preferable to have the bottom plate 31 horizontal and without any inclination. However, this would prevent solids from being transported toward the weir 37 due to their own weight. Therefore, when removing solids, the valve (not shown) of the solids extraction pipe 41 is opened to discharge all of the treated water accumulated in the treatment tank 30. Then, while the wastewater is still being sprayed onto the trickling filter bed, the treated water that passes through the filter bed and drips into the treatment tank 30 is showered, allowing the accumulated solids on the bottom plate 31 to be transported toward the weir 37 along with the treated water, even at a gentle incline close to horizontal. Once the solids are no longer present on the bottom plate 31, the valve of the solids extraction pipe 41 is closed, and the treated water is stored in the treatment tank 30. Considering these factors, the inclination angle is preferably 1 / 100 to 15 / 100, and more preferably 5 / 100 to 10 / 100. If the inclination angle is less than 1 / 100, showering of treated water dripping into the treatment tank 30 tends to deposit solids on the bottom plate 31 instead of sending them toward the weir 37. Furthermore, if the inclination angle exceeds 15 / 100, the height of the treatment tank 30 becomes too large. To incorporate the trickling filter device 1 within the dimensions regulated for marine transport containers, the height of the trickling filter reaction tank (20) must be lowered, resulting in a smaller reaction tank capacity and reduced purification capacity. For example, the external dimensions of a 10-foot marine transport container are 2,991 mm long, 2,438 mm wide, and 2,591 mm high, and the height must be kept within 2,591 mm.The height of 12, 20, and 40-foot types is also restricted to 2,591 mm.

[0013] The water tank section 36 is provided with a weir 37 that holds back the treated water accumulated in the treatment water tank 30. During normal operation, the treated water that slips under the weir 37 flows into the water tank section 36 and is discharged through a treated water withdrawal pipe 40. The water tank section 36 is also provided with an air withdrawal pipe 38 that draws air out of the treatment water tank 30. The tip 38a of the air withdrawal pipe 38 is positioned above the water surface 39 of the treated water stored in the water tank section 36. As the area below the tip 38a is sealed with treated water, when air is drawn in by a fan (not shown) or the like, the air passes through the reaction tank 20 from the top and enters the air withdrawal pipe 38, and at the same time, putrid odors in the treatment water tank 30 are discharged. As described above, when air is drawn in through the air vent pipe 38, air enters the air vent pipe 38 from the top of the reaction tank 20, and at the same time, air etc. is supplied to the sponge carrier 23 inside the housing 21 of the reaction tank 20.

[0014] The water tank section 36 is provided with a solids extraction pipe 41 for extracting treated water and solids accumulated in the water tank section 36. The solids extraction pipe 41 is used to extract solids that accumulate on the sloped portion of the bottom plate 31 during operation of the container-type trickling filter. In the container-type trickling filter apparatus 1 configured as described above, solids that accumulate on the sloped portion of the bottom plate 31 are extracted together with treated water through the solids extraction pipe 41 during operation. When the treated water tank 30 is emptied of treated water, treated water drips from above the reaction tank 20 and falls like rain, allowing solids that accumulated on the bottom plate 31 when the treated water was extracted to be thoroughly washed away. As described above, the container-type trickling filter apparatus of the present invention does not require a mechanical discharge device such as a scraper, as in the conventional container-type trickling filter apparatus. Therefore, solids do not accumulate when the solids are extracted, and the treated water tank can be thoroughly cleaned and the accumulated solids can be discharged.

[0015] In the container-type trickling filter apparatus 1 of this embodiment, the water tank section 36, which collects and discharges treated water and solids such as sludge in the lower treated water tank 30, is configured to be horizontally outboard of the container-type trickling filter apparatus 1. This is because the structure provides ample space for an inspection hatch 27 for inspecting the inside of the reactor and for a ladder 26 that can be moved toward the top of the apparatus and used for inspection work. In another embodiment, as shown in Figure 8, the reactor capacity may be increased so that the inspection hatch 27 for inspecting the inside of the reactor and the ladder 26 for inspection work fit within the dimensional restrictions of marine transport containers, and the water tank section 36 may be configured to be horizontally inboard of the container-type trickling filter apparatus 1 to maximize the performance of the container-type trickling filter.

[0016] FIG. 6 shows an embodiment in which a circulating treated water withdrawal pipe 42 is provided to circulate treated water to the wastewater supply side piping of the container-type trickling filter device 1 using a pump (not shown) to remove nitrogen from the wastewater. Ammonia in the wastewater is nitrified in the aerobic reaction tank 20, and treated water containing nitrate nitrogen is circulated to the reaction tank 20. Nitrogen is removed by denitrification using the action of denitrifying bacteria, which are facultative anaerobic bacteria present in the reaction tank 20. The treated water withdrawal pipe 40 and the circulating treated water withdrawal pipe 42 are connected to an overflow trough 43. A partition plate 44 is movably installed between the treated water withdrawal pipe 40 and the circulating treated water withdrawal pipe 42 in the overflow trough 43. The installation position of the partition plate 44 is adjustable in the direction of the arrow in the figure to determine the amount of circulating treated water. That is, when the nitrogen removal rate needs to be increased, the partition plate 44 is moved closer to the treated water withdrawal pipe 40 to increase the amount of circulating treated water. On the other hand, when it is not necessary to increase the nitrogen removal rate, the partition plate 44 is moved closer to the circulating treated water withdrawal pipe 42 to reduce the amount of circulating treated water.

[0017] 9 shows another embodiment of the container-type trickling filter apparatus 1 of the present invention. If the inside of the air withdrawal pipe 38 becomes wet and condenses, a pool of water will form. If a fan or other device (not shown) is used for suction, the fan may be damaged by sucking in the water. Therefore, a drain pipe 45 is provided midway through the air withdrawal pipe 38 so that the pool of water inside the air withdrawal pipe 38 is discharged into the treated water withdrawal pipe 40. The discharge destination is not limited to the treated water withdrawal pipe 40, but may also be the solids withdrawal pipe 41, or the drain pipe 45 may be connected by drilling a hole in the side wall 32 of the water tank section 36.

[0018] 10 is a diagram showing another embodiment of the container-type trickling filter device 1 of the present invention, in which the air vent pipe 38 is inclined so that the tip 38a of the air vent pipe 38 is downward. This allows dew water generated in the air vent pipe 38 to be discharged into the treated water tank 30, preventing water from pooling in the air vent pipe 38.

[0019] 11 to 13 are diagrams showing other embodiments of the container-type trickling filter apparatus of the present invention. FIG. 11 is a diagram showing the configuration of the reaction tank 20. FIG. 12 shows an embodiment in which the treated water tank 30 of the container-type trickling filter apparatus 1 shown in FIG. 1 is made of a civil engineering structure such as concrete. In this example, within the dimensional restrictions of marine transport containers, the space occupied by the treated water tank 30 in FIG. 1 can be replaced with the capacity of the reaction tank 20 of the container-type trickling filter apparatus 1, thereby increasing the capacity. Furthermore, since deposits on the gently sloping bottom plate 31 can be removed by showering, the height of the container-type trickling filter apparatus 1 can be reduced, resulting in a more compact design. Therefore, while improving purification capacity by increasing the capacity of the container-type trickling filter apparatus 1, the vertical space required for the container-type trickling filter apparatus 1 can be reduced.

[0020] In FIG. 13, similarly to FIG. 12, the treated water tank 30 is a civil engineering structure, and the reaction tanks 20 are stacked in two stages.

[0021] As shown in Figures 12 and 13, the reaction tank 20 is composed of multiple housings 21, and the height and volume of the container-type trickling filter device 1 can be changed by increasing the number of housings 21 horizontally or changing the number of housings 21 vertically.

[0022] In the embodiment of the present invention, a marine transport container is used for the outer frame (51-54) of the container-type trickling filter bed device, but this is not limited to this, and the feature of the present invention lies in the structure of the lower treated water tank in the container-type trickling filter bed device.

[0023] 1: Container-type trickling filter device 20: Reaction tank 21: Housing 22: Bottom plate 23: Sponge carrier 26: Ladder 27: Inspection hatch 30: Treated water tank 30A: Main body 31: Bottom plate 32-35: Side walls 36: Water tank section 37: Weir 38: Air withdrawal pipe 40: Treated water withdrawal pipe 41: Solids withdrawal pipe 42: Circulating treated water withdrawal pipe 43: Overflow trough 44: Partition plate 45: Drain pipe 50: Civil engineering structure

Claims

1. A trickling bed device (1) comprising a reaction tank (20) and a treated water tank (30), wherein the reaction tank (20) comprises an airtight rectangular parallelepiped housing (21), a mesh-like bottom plate (22) attached to the bottom of the housing (21), and carriers (23) packed inside the housing (21), and the treated water tank (30) comprises a box-shaped main body (30A) comprising a rectangular bottom plate (31) inclined in the direction of discharge of treated water and side walls (32-35), a water tank section (36) attached to the main body (30A) in the direction of discharge of treated water, a weir (37) attached to the water tank section (36), an air withdrawal pipe (38), a treated water withdrawal pipe (40), and a solids withdrawal pipe (41).

2. A container-type trickling filter device according to claim 1, characterized in that a treated water withdrawal pipe (42) for circulation is provided in the water tank section (36).

3. A container-type trickling filter device as described in claim 2, characterized in that an overflow trough (43) is provided in the treated water tank (30), and a partition plate (44) is movably provided between the treated water withdrawal pipe (40) connected to the overflow trough (43) and the circulating treated water withdrawal pipe (42).

4. A container-type trickling filter device as described in any one of claims 1 to 3, characterized in that a drain pipe (45) for discharging water pools from within the air extraction pipe (38) is provided midway along the air extraction pipe (38).

5. A container-type trickling filter device as described in any one of claims 1 to 4, characterized in that the air extraction pipe (38) is inclined so that the tip (38a) of the air extraction pipe (38) is downward.

6. A container-type trickling filter device as described in any one of claims 1 to 5, characterized in that the bottom plate (31) of the treated water tank (30) has a slope of at least 1 / 100 toward the discharge section of the treated water.

7. A container-type trickling filter device as described in any one of claims 1 to 6, characterized in that the treated water tank (30) of the trickling filter device (1) is made into a civil engineering structure, and the space occupied by the treated water tank (30) is replaced and increased by the capacity of the reaction tank (20) of the trickling filter device (1) within the dimensional regulations for marine transport containers.

8. A container-type trickling filter device as described in claim 7, characterized in that the reaction tank (20) is composed of multiple stages of the housings (21), and the height and volume of the trickling filter device (1) can be changed by changing the number of the housings (21).

9. A method for cleaning the treated water tank (30) of a container-type trickling filter bed apparatus described in any one of claims 1 to 8, characterized in that when extracting solids, the valve of the solids extraction pipe (41) is opened to discharge all of the treated water accumulated in the treated water tank (30), and then, while the wastewater is being sprayed onto the trickling filter bed, the treated water that passes through the filter bed and drips into the treated water tank (30) is showered to send the accumulated solids on the bottom plate (31) together with the treated water toward the weir (37) even at a gentle incline that is nearly horizontal.

Images